Genetically enabling Hydra oligactis for comparative studies in development, regeneration and aging.

PROJECT SUMMARY The small freshwater cnidarian Hydra has played a crucial role in several scientific breakthroughs, most notably being the first animal where regeneration was discovered in 1744. Over the years, different Hydra species contributed to fundamental findings, but Hydra vulgaris has become the standard "Hydra model" in

modern molecular research. With a chromosome-level genome assembly and tools to test gene function, H. vulgaris is a prime model for developmental and regenerative biology but is also an emerging model in various fields including neuroscience and microbiome research. In contrast, Hydra oligactis, another Hydra species,

remains underutilized despite its biologically relevant distinct features. Unlike H. vulgaris, H. oligactis exhibits deficiencies in regenerating its aboral end and undergoes senescence and death upon gamete production. The sharp contrasts between these closely related species offer a unique comparative platform for

exploring molecular mechanisms in regeneration and aging. Despite being behind in tools and resources, H. oligactis can be reliably cultured, making it a promising candidate for functional studies. Completion of the proposed aims will bridge the gap between the two species: 1. Build Genomic and Transcriptomic Resources: Develop a chromosome-scale genome assembly with

gene regulatory annotations, and a single-cell expression atlas for H. oligactis, paralleling the resources available for H. vulgaris. 2. Implement Transgenesis and siRNA Knockdown: Establish transgenesis in H. oligactis and create transgenic lines that express fluorescent proteins in specific lineages. These lines will enable the

optimization of gene knockdown through siRNA electroporation. 3. Develop CRISPR Gene Editing: Utilize the inducible egg production in H. oligactis to troubleshoot CRISPR-Cas9 mediated gene editing. The immediate goal is to tag the endogenous EF1-alpha gene, a strategy that will inform future gene editing attempts in both H. oligactis and H. vulgaris.

The completion of these aims will equip H. oligactis with tools and resources comparable to H. vulgaris, enabling functional studies and comparative analyses. This comparative approach holds potential implications for various scientific fields, including developmental and regenerative biology, aging, neuroscience,

microbiome research, and biophysics. This project is therefore highly responsive to the FOA (PAR-21-167), which calls for the development and improvement of animal models that are relevant to multiple NIH Institutes.